The present invention relates generally to methods and apparatus for controlling flow in a pump. More particularly, the present invention relates to suction and discharge valves for reciprocating pumps used to pump abrasive fluids.
Suction and discharge valves are used in reciprocating pumps to control the flow of fluid into and out of the cylinders in which the fluid is pressurized. Reciprocating pumps are used in various operations to pressurize an often abrasive slurry mixture of solids and liquids. For example, reciprocating pumps are used in drilling operations to pressurize a slurry mixture of solids and liquids known as drilling mud to the bottom of a hole drilled into the earth. The pressurized mud is used to lubricate and cool a downhole drill bit as well as to carry loosened sediment and rock cuttings back to the surface. At the surface, the cuttings and sediment are removed from the returning drilling mud for examination and the filtered drilling mud is able to be reused. In many cases, highly abrasive particles are present in the fluids that are being pumped through the system.
Because of these highly abrasive components, valves and seals of reciprocating pumps must be designed to resist harsh abrasion, while maintaining positive sealing action and withstanding high operating pressures. Due to the abrasive and corrosive nature of most drilling fluids, these valves have a finite service life and must be replaced when the leakage rate increases to a point that the pump will not maintain satisfactory pressure for the drilling conditions. These valves and seats normally fail due to a deterioration of the elastomer sealing element of the valve, erosion cause by fluid cutting of the valve and seat metal contact surfaces or a combination of these two. Because the maintenance of these valves is a time consuming and expensive process, valves having an increased service life are desirable.
Thus, there remains a need to develop methods and apparatus for suction and discharge valves, which overcome some of the foregoing difficulties while providing more advantageous overall results.